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Fukushima Nuclear Accident Update Log

Updates of 8 April 2011

IAEA Incident Emergency Centre (IEC)

IAEA Briefing on Fukushima Nuclear Accident (8 April 2011, 15:00 UTC)

Summary of Reactor Status

On Friday, 8 April 2011, the IAEA provided the following information on the current status of nuclear safety in Japan:

1. Earthquake of 7 April

The IAEA confirms that an earthquake occurred in Japan at 14:32 UTC, 7 April. The IAEA International Seismic Safety Centre has rated it as a 7.1 magnitude, revised from an initial 7.4 magnitude. The epicenter of the earthquake was 20 km from the Onagawa nuclear power plant and approximately 120 km from the Fukushima Daiichi and Daini nuclear power plants.

The IAEA has been in contact with NISA and can confirm the status of the following nuclear facilities:

Fukushima Daiichi Nuclear Power Plant

No changes have been observed at the on-site radiation monitoring posts. The injection of water into the reactor pressure vessels of Units 1, 2 and 3 was not interrupted.

Fukushima Daini Nuclear Power Plant

No changes have been observed of the readings at the on-site radiation monitoring posts.

Onagawa Nuclear Power Plant

All reactors have been in cold shutdown since 11 March earthquake.

Two out of the three lines supplying off-site power to the site were lost following the 7 April earthquake. Off-site power continues to be supplied through the third line.

Cooling of the spent fuel pool was temporarily lost, but has subsequently been restored.

No change has been observed in the readings from the on-site radiation monitoring post. The status of the plant is currently being checked.

Tokai Daini Nuclear Power Plant

Tokai Daini nuclear power plant remains in cold shutdown since the 11 March earthquake. No abnormality has been observed.

Higashidori Nuclear Power Plant

The Higashidori nuclear power plant was shut down and in a maintenance outage at the time of the 7 April earthquake. Off-site power was lost temporarily. Emergency power supply to the site operated as expected until off-site power was restored. All the fuel had been removed from the reactor core and stored in the spent fuel pool. Cooling of the spent fuel pool is operational.

Tomari Nuclear Power Plant (in Hokkaido)

At the time of the 7 April earthquake Tomari Unit 1 and Unit 2 were in operation. Following the 7 April earthquake, the Hokkaido Electric Power Company reduced the generating power to 90% of capacity.

Rokkasho Reprocessing Plant

The Rokkasho Reprocessing Plant and uranium enrichment facility lost off-site power. Emergency power supply to the site is operating.

2. Current Situation

Overall, the situation at the Fukushima Daiichi plant remains very serious although there are early signs of recovery in some functions such as electrical power and instrumentation.

As of 6 April, TEPCO started injecting nitrogen gas to Unit 1 containment vessel to reduce the possibility of hydrogen combustion within the containment vessel.

The leakage of highly contaminated water from the 20 cm crack in the cable storage pit of Unit 2 directly to the sea reported on 2 April was stopped by injection of coagulation agents (liquid glass) on 5 April. Additional activities to secure the leak were reported finished on 6 April.

To prevent discharge of contaminated water from the Fukushima Plant to the open sea, construction work was carried out at the breakwater in the southern part of the Plant on 5 April.

In Unit 1 fresh water has been continuously injected into the reactor pressure vessel through feed-water line at an indicated flow rate of 6 m3/h using a temporary electric pump with off-site power. In Units 2 and 3 fresh water is being injected into the reactor pressure vessels continuously through the fire extinguisher lines at indicated rates of 8 m3/h and 7 m3/h using temporary electric pumps with off-site power.

The reactor pressure vessels' temperatures remain above cold shutdown conditions (normally less than 95 °C). In Unit 1 indicated temperature at the feed water nozzle of the RPV is 224 °C and at the bottom of RPV is 117 °C. The pressure in the RPV is increasing as indicated on both channels of instrumentation. NISA has indicated that some instruments in the reactor vessel may not be working properly. Drywell pressure is increasing slightly due to the addition of nitrogen. In Unit 2 the indicated temperature at the feed water nozzle of the RPV is 144 °C. The temperature at the bottom of RPV was not reported. Indicated Drywell pressure remains at atmospheric pressure. In Unit 3 the indicated temperature at the feed water nozzle of the RPV is 88 °C and at the bottom of RPV is 112 °C. Fresh water was sprayed onto the spent fuel pool by concrete pump vehicle (50t/h) from 21:53 UTC, 6 April.

No change in status in Units 4, 5 and 6 and the Common Spent Fuel Storage Facility.

2. Radiation Monitoring

On 7 April, low levels of deposition of both iodine-131 and cesium-137 were detected in 5 and 4 prefectures respectively. The values reported for iodine-131 ranged from 3.8 to 20 becquerel per square metre, for cesium-137 from 9.7 to 25 becquerel per square metre.

Gamma dose rates continue to decrease. For Fukushima, on 7 April a dose rate of 2.3 µSv/h, for the Ibaraki prefecture a gamma dose rate of 0.16 µSv/h was reported. Dose rates reported for the Eastern part of the Fukushima prefecture, for distances of more than 30 km to Fukushima-Daiichi, range from 0.2 to 28 µSv/h.

As part of a new measurement program carried out by MEXT in cooperation with universities, gamma dose rates have also been measured in 26 cities in 13 prefectures for the period 5 to 7 April. In 19 cities, all measurements are below 0.1µSv/h. In a further five cities, some measurements are up to 0.21µSv/h. In the city of Tsukuba in the prefecture of Ibaraki, dose rates are in the range 0.17 to 0.2 0 µSv/h. In Fukushima City, the range is 0.42 to 0.5 µSv/h. typical normal background levels are in the range 0.05 to 0.1 µSv/h.

As of 6 April, iodine-131 and cesium-137 was detectable in drinking water in a few prefectures at levels far below those that would initiate recommendations for restrictions of drinking water. As of 7 April, one restriction for infants related to I-131 (100 Bq/l) remains in place as a precautionary measure in only one village of the Fukushima prefecture.

Since our written briefing of yesterday, data related to food contamination was reported on 7 April by the Japanese Ministry of Health, Labour and Welfare. These reported analytical results covered a total of 63 samples taken from 5 - 7 April. Analytical results for 62 of the 63 samples for various vegetables, spinach and other leafy vegetables, various meats, unprocessed raw milk and seafood in nine prefectures (Chiba, Fukushima, Gunma, Hyogo, Ibaraki, Kanagawa, Niigata, Tochigi and Yamagata) indicated that I-131, Cs-134 and/or Cs-137 were either not detected or were below the regulation values set by the Japanese authorities. One sample of spinach (grown outdoors) taken on 6 April in Ibaraki prefecture was above the regulation value set by the Japanese authorities for I-131.

TEPCO is conducting a programme for seawater (surface sampling) at a number of near-shore and off-shore monitoring locations. The near-shore sampling point for Daiichi Units 1 - 4 is located 330 m south of their common discharge point. The near-shore sampling point for Daiichi Units 5 and 6 is located 30 m north of their common discharge point.

Until 3 April a general decreasing trend was observed at these sampling points. After the discharge of contaminated water on 4 April, a temporary increase has been reported. On 5 April a decrease was again observed at these points.

At the Daini site, near-shore samples are being collected at two locations: directly north of the common discharge point of Daini, and close to Iwasawa Beach, which is south of Daini nuclear power plant. The latter monitoring point is 16 km south of Daiichi nuclear power plant on the northern boundary of TEPCO's Hirono thermal power plant. Starting from 2 April, TEPCO collected samples at three additional sampling points lying on a north-south transect that runs parallel to the coast but at a distance of 15 km from the shore. On 4 April, a further set of three sampling points, also at 15 km from the shore, was added. All six sampling locations lie along a north-south transect.

Since 5 April TEPCO is sampling daily at 6 points situated 15 km offshore along a north-south transect. Levels of radionuclides reported at these locations for 5 of April are in the range 57 - 200 Bq/l for I-131, 57 - 310 Bq/l for Cs-134 and 18 - 320 Bq/l for Cs-137. Values of Cs-134 and Cs-137 measured at the sampling points situated at the North and South ends of the transect are considerably lower than those measured at the stations directly offshore from the release points.

MEXT initiated the off-shore monitoring program on 23 March. Initially, the monitoring was carried out at 8 points lying on a north-south transect parallel to the coast and 30 km off-shore. Sampling points 1 to 8 are separated by about 10 km. On 28 March, points 9 and 10 were added to the off-shore sampling scheme. Points 8, 9 and 10 lie in one line perpendicular to the coast. Points 8 to 10 are also separated by 10 km. On 4 of April MEXT added two sampling points to the north-west of sampling point 1. These are referred as point A and B. Monitoring at off-shore points consist of:

  • Measurements of ambient dose rate in air;
  • Collection and analysis of surface sample of seawater; and
  • Collection and analysis of samples of sea water collected 10 metres above the sea water bottom.

On 8 April the only data reported concerned the 15 km offshore north-south transect.

4. IAEA Activities

A team of three Agency experts in BWR technology continue to meet with TEPCO and NISA officials in Tokyo and are expected to be back in Vienna on 13 April 2011.

In addition to those reported in previous briefs the following countries have submitted monitoring data and/or links to national websites where data is available: Denmark, Germany, Lithuania, Luxembourg, Mexico and Portugal.